The last time the US National Debt decreased (slightly) was between 1959 and 1960.

Clinton's best year was 2000 when he had an $18 billion deficit. This good show was caused by a huge boom in federal revenue from "dot.com" stock value explosion (to a large extent).

What followed was a serious drop in federal revenue:

          $2,025 trillion total federal revenue ~ 2000

          $1,798 trillion total federal revenue ~ 2004

That drop in revenue would increase the National Debt by $227 billion (annually) even if spending did not go up.